Radio receiving system



July 12, 1932. p w L 1,866,916

RADIO RECEIVING SYSTEM Original Filed April 23, 1924 2 Sheets-Sheet l INLfENTOR.

July 12, 1932. P. G. WEILLER I 1,866,916

RADIO RECEIVING SYSTEM Original Filed April 25, 1924 2 Sheets-Sheet 2 IN V ENTOR.

@ M ATTORNEY Patented July 12, 1932 UNITED STATES PATENT OFFICE ram. 6. WEILLER, or EAST onANen, NEW JnnsEY, Ass enon TO WIRED RADIO, me, on

NEW YoRK, n. Y., A conroRA'rIoN' or nnnawann nanro nncnrvnve SYSTEM Original application filed April 23,193, Serial No. 708,341. Iatent No. 1,684,164, dated September 11,

' i 1928. Divided and this application filed. August 2, 1928. Serial No. 296,97;

This invention relates to the reception of wireless telephone and telegraph signals by means of'vacuum tubes and associated tuning circuits.

This application is a division of my application Serial No. 7 08,341, filed April 23, 1924, entitled Radio reception, now Patent No. 1,684,164, issued September 11, 1928.

It is the object of the present invention to provide an improved circuit arrangement for the reception of wireless signals whereby selectivity and ease of control are greatly increased and distortion of the received signal is materially reduced.

In this improved form of receiver vacuum tubes of the three-electrode type are employed. An inductance is connected in the usual manner in the grid-filament circuit, and this inductance is closely coupled to another inductance of approximately the same value which is connected at one end to the plate of the vacuum tube. WVhen this inductance is connected directly to the plate, the telephones and source of energy for the plate circuit are connected between the filament and plate in the usual manner. The tuning of the grid and plate circuits is preferably accomplished by means of a single variable condenser which is connected either across the grid inductance or across the plate inductance. It is possible for this single condenser to tune both circuits simultaneously by virtue of the close coupling of the grid and plate inductances. The incoming energy is supplied to the grid circuit through an inductance which is loosely coupled to the combined grid-plate inductances. This loosely coupled inductance may be in the antenna circuitor other circuit from which the energy to be received is supplied.

If the relative values of the component parts of these receivers are correct, the vacuum tube will normally oscillate, and the variation of the single condenser will serve to vary the frequency of the oscillations. The

" variation of the coupling between the antenna inductance and the grid inductance will serve to control the oscillations in the vacuum tube circuits, but will not materially vary the tuning of these circuits if the inductive and capacity coupling between the antenna inductance and the grid inductance is sufficiently small. Better control of the oscillationsis ob tained by coupling to either the grid or the plate inductance, or both, an inductance shunted by a variable high resistance. hen the resistance is adjusted'to the correct value oscillation of the tube will cease, but the received signal intensity will be undiminished. Apparently any absorption of energy by this control circuit is offset by the increased voltage on the grid due to'change in phase between the'received voltage and current caused by the resistance.

In order to receive a signal of an unknown wave length with this receiver, the single variable condenser is varied until the characteristic beat notes of autodyne reception are heard, and the condenser is then set so that the receiver is tuned between the beat notes of the received signal. The antenna circuit is then tuned until the maximum of energy is received. The antenna coupling may then be varied until the oscillation of the receiver ceases. Or the oscillation of the receiver can be eliminated by adjusting the resistance across the inductance associated with the grid or plate circuit until the correct value is found. '7

The ordinary regenerative receiver when tuned by the zero beat method, that is, when both plate and grid circuits are tuned alike is extremely critical, and ives great distortion of the received signal. 'Vith the present circuit,"however, there is no ditficulty in tuning, as there is but one tuning control, aside from any antenna tuning that may be provided, and the other control serves merely to elimi' nat'e the oscillation which causes the distortion in ail-"ordinary regenerative receiver.

This inventionis readily adapted to radio frequency amplification, and makes such'amplifica'tion possible without distortion or disturbing oscillation. The change from the circuit just described is small. A choke coil is substituted for the telephones, and "either end of the plate 1 inductance is connected through a condenser to the grid of another vacuum tube which may be used as a detector. In this circuit arrangement .it is particularly advisable to utilize an inductance associated with the grid or plate inductance of the radio frequency tube and shunted by avariable high resistance to control the oscillations of the radio frequency tube and thus prevent distortion. I

It has been found that particularly good operation can be obtained with the specially wound coils disclosed in my Patent No. 1,684,164 and described hereinafter wherein the grid and plate coils are simultaneously wound on the same form but it is to be understood that the invention is not limited to this particular embodiment.

A clearer understanding of the invention may be had from the following description of the preferred embodiment illustrated in the accompanying drawings.

In these drawings,

Fig. 1 is a circuit diagram of a vacuum tube receiver associated with an antenna receiving circuit and utilizing the variable coupling between the antenna circuit and the grid-plate circuit to control the oscillations of the receiver;

Fig. 2 illustrates a modification of this circuit arrangement in which a control circuit is associated with the plate and grid inductances of the receiver to control the oscillations;

Fig. 3 is a circuit diagram illustrating an application of this invention to a radio frequency amplifier;

Fig. 4 illustrates in detail apreferred form of winding for the closely coupled grid and plate coils;

Fig. 5 illustrates the completely wound grid and plate coils; and

'Fig. 6 shows the antenna inductance coupled to the combined grid and plate inductances and means for varying the coupling between these circuits.

In the circuit diagram of Fig. 1, 2 and 3 represent the filament grid, and plate respectively of the vacuum tube. The grid 2 is connected to the filament 1 through an inductance 4. An inductance 5 is closely coupled to the inductance 4, preferably with an inductive coupling of approximately 80%. One end of this inductance is connected to the plate 3, and the other end is connected merely to one side of the condenser 6, which is shunted across the inductance without changing the operating characteristics of the circuit or departing from this invention.

\ The amount of impedance inthe telephone circuit 7 is important, and should be at least equal to that afforded by a pair of ordinary 2000 ohm phones. The antenna circuit includes an inductance 8 which is very loosely coupled to the inductances 4 and 5, and also a variable condenser 9 which serves to tune the antenna circuit.

By experimenting it has been found that the following values for the component parts of this receiving circuit give good operating has been found to be better in operation.

characteristics for the reception of wave lengths between 250 and 600 meters: grid and plate inductances (4t and 5), 0.22 millihenries; coupling between grid and plate inductances, 80% inductive; capacity between grid and plate inductances, approximately 25 micromicrofarads; condenser (6), 0.0005 microfarads. The antenna inductance may be of any value convenient for the wave length range desired. In one embodiment it was 0.389 millihenries.

These values for the component parts are such that with a commercial vacuum tube the grid circuit will always be exactly tuned to the plate circuit, or at least nearly enough so that, because of the feedback relation between the grid and plate circuit, oscillations will take place for any setting of the condenser 6 unless other adjustments are made to prevent. them.

To receive av signal of an unknown wave length, the inductance 8 is coupled to the inductances 4 and 5 a little more closely than normally, and the condenser 6 is varied until the two characteristic beat notes of the station to be received are heard. The condenser is then set so that the receiver is tuned between the two beat notes. Under these conditions the receiver is oscillating at the frequency of the received signal and fair reception will be obtained. The final adjustment is made by tuning the antenna circuit by means of condenser 9 or by varying the coupling of the antenna inductance until the os cillations disappear.

The arrangement illustrated in Fig. 2 is designed to accomplish the same results, but The component parts have been marked with corresponding characters, and it will be noted that in this embodiment the condenser 6a is across the grid inductance 4a and that the plate inductance 5a has one free end. This circuit arrangement also differs from the preceding one in that, coupled with the plate and grid inductances, there is an inductance l0 shunted by a high variable resistance 11. The operation of this receiver is the same as that illustrated in the preceding figure with the exception that in order to eliminate the undesirable oscillations, the resistance 11 is varied until the setting is found at which the oscillations will. disappear. It has been found that although the setting of this resistance is not critical, best results are obtained at a particular value. Values either higher or lower than this optimum value will cause oscillations to appear in the circuits.

An application of my invention to a radio frequency circuit is illustrated in Fig. 3, in which the parts which are similar to those of Fig. 1 are indicated by corresponding nuand the plate to permit the flow of direct current through the plate circuit but exclude the high frequency currents. In order to indicate the received signal, the grid of a detector tube 13 is connected through a condenser 14 to the plate 35 of the radio frequency tube. Alternatively it may be connected to the end 15 of inductance 5b as shown in Fig. 3a. This detector tube may be associated with operative circuits in any of the usual manners, only one of many forms being illustrated. In operation the radio frequency amplifier is essentially the same as the other two receivers previously described. The signal to be received is located by varying the condenser 66 and setting it between the two characteristic beat notes, the indication being given in the telephones connected in the plate circuit of the detector tube 13. The oscillations of the circuits are then eliminated by varying either the coupling of the inductance 8b with the inductances 4b and 5?) or by varying the resistance 11?) across the inductance 106.

It has been found that the operating characteristics of the circuit are especially good when the inductances are wound as illustrated in Fig. 4. Diagonal slots such as 16 of Fig. 4 (16, 17, 18, 19 of Fig. 5) are cut in a dielectric frame 20. The two coils are then wound on this framework in the manner illustrated in Fig. 4. The winding of the grid coil 4, for example, is begun at 21, and the winding of the plate coil 5 is begun on the opposite side of the frame but close to the 1 grid coil. When the slot 16 is reached, the

coil 4 is lead through the slot and continues along the obverse side of the frame, whereas the coil 5 is led through the slot and continues along the reverse side of the frame.

? When the slot 17 is reached, the opposite procedure takes place and the coils are thus wound side by side but on opposite sides of the framework. 7 The winding thus continues until the desired amount of inductance is l wound on the frame. It has been found that this method of winding gives a Very compact inductance element in which the inductive coupling is approximately 80% and the capacity coupling is suflicient to give the desired characteristics to the plate and grid cirductances 23 and the antenna inductance 24 are mounted. The antenna inductance 24 is placed at right angles to the inductances 23 and is hinged at the bottom to permit of movement with respect to the inductance 23. This movement is secured by means of a small cord 25 which is wound on a reel 26 preferably controlled from the outside of the cabinet by means of a knob 27. The spring 28 tends to maintain the inductance 24 in its normal vertical position. This arrangement of apparatus has been found to give particularly good results, but it is not intended to limit the present invention in any way to the embodiment illustrated.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. In a radio receiving system, an electron tube having cathode, grid and plate, an antenna circuit, a grid inductance connected between said grid and cathode, a tuned circuit comprising a second inductance shunted by a variable condenser, said second inductance being coupled to said grid inductance, and both of said grid inductance and said second inductance being coupled to said antenna circuit, said tuned circuit being connected to other elements of said system by a single conductor connected to said plate whereby both of said inductances may be tuned simultaneously.

2. In a radio receiving system, anelectron tube having cathode, grid and plate, a grid inductance connected between said grid and cathode, a plate inductance connected to said plate by a single conductor, said grid inductance being closely coupled to said plate inductance, and a variable condenser connected in shunt across one of said inductances, whereby the circuit of said grid and the circuit of said plate may be tuned simultaneously.

3. In a radio receiving system, an electron tube having cathode, grid and plate, a grid inductance connected between said grid and cathode, a Variable condenser connected in shunt across said grid inductance, a plate inductance coupled closely to said grid inductance and connected to the other elements of said system by a single conductor connectedto said plate, whereby the circuit of said grid and the circuit of said plate may be tuned simultaneously.

4. In a radio receiving system, an electron tubehaving cathode, grid and plate, a grid inductance connected between said grid and cathode, a variable condenser connected in shunt across said grid inductance, an output circuit connected between said plate and said cathode, and a plate inductance coupled closely to said grid inductance and connected to the other elements of said system by a single conductor connected to said plate, whereby the circuit of said grid and the circuit of said'plate may be tuned simultaneously. V

5. In a radio receiving system, an electron tube having cathode, grid and plate, a grid inductance connected between said grid and cathode, a variable condenser connected in shunt across said grid inductance, a plate inductance coupled closely tosaid grid inductance and connected to the other elements of said system by. a single conductor connected to said plate, and a damping circuit comprising a damping inductance shunted by a resistance, said damping inductance being coupled to said grid and plate inductances whereby the circuit ofsaid grid and the circuit of said plate may be tuned simultaneously.

6. In a radio receiving system, an electron tube having cathode, grid and plate, a grid inductance connected between said grid and cathode, a variable condenser connected in shunt across said grid inductance, a plate 1nductance coupled closely to said grid induc-' tance and connected to the other elements of said system by a single conductor connected to said plate, and an antenna circuit loosely coupled to said inductances, whereby the circuit of said. grid and the circuit of said plate may be tuned simultaneously.

7. In a radio receiving system, an electron tube having cathode, grid and plate, an antenna circuit, a grid inductance connected between said grid and cathode, a tuned circuit comprising a second inductance shunted by a variable condenser, said second inductance being coupled to said grid inductance,

and both said grid inductance and said second inductance being coupled to said antenna circuit, said tuned circuit being connected to the other elements of said system by a single conductor connected to said plate, and a second electron tube having its input circuit connected by a single conductor to a point in said tuned circuit, whereby the circuit of said grid and the circuit of said plate may be tuned simultaneously.

8. In a radio receiving system, an electron tube having cathode, grid and plate, a grid inductance connected between said grid and cathode, a plate inductance connected to said plate by a single conductor, said grid inductance being closely coupled to said plate inductance, said grid inductance and plate inductance comprising a flat support having an even number of substantially radially disosed slots a rid windinir and a alate winding engaged in said slots with the turns of one overlying the turns of the other and disposed at opposite sides of said support, and a variable condenser connected in shunt across one of said inductances, whereby the circuit of said grid and the circuit of said plate may be tuned simultaneously.-

In testimony whereof I afiix my signature.

PAUL Gr. WEILLER. 

